Help c++ global varibles

Elfman

Hi im doing a project in c++ I'm using global varibles in a header file called global.h all the varibes are ints . I keep gettign an eorroe message saying

"(?gbl"Varible name") already defined in "obj name"

can anyone tell me whats i'm doing wrong cheers all

-Elfman

satchmo

That's caused by more than one translation unit including global.h, and so when they're linked together the same variables are defined twice and so the linker throws that error. You can get around it by using 'inclusion guards'... basically put the code

#ifndef GLOBAL_H
#define GLOBAL_H

at the top of global.h, and

#endif

at the bottom. That way the preprocessor will only include the code in global.h once, and you won't get duplicate variables.

You should read this article, it explains the whole header/implementation file split pretty well.

Tobias Greeshman

Along with already stated you can include the following line under the preprocessor lines (inclusion guards). It effectively does the same, by only permitting the header file to be included once, thus the code is not compiled multiple times.

#pragma once